An organic light-emitting device includes an anode, a cathode, and an organic-compound layer interposed between the two electrodes. An organic light-emitting device is also referred to as organic electroluminescent (EL) device. In an organic light-emitting device, excitons are generated by the recombination of positive holes (holes) and electrons injected from the respective electrodes in the organic-compound layer, and the excitons emit light upon transition to the ground state. There have recently been remarkable advances in organic light-emitting devices. Thus, thin, lightweight light-emitting devices having a low drive voltage, various emission wavelengths, and fast responsibility are available.
Among the organic light-emitting devices, a phosphorescent light-emitting device includes a phosphorescent light-emitting material in the organic-compound layer and emits light caused by triplet excitons. There is still room for improvements of the luminous efficiency and the operating life of phosphorescent light-emitting devices. Thus, improvement of the emission quantum yield of phosphorescent light-emitting materials and suppression of degradation of the structure of the molecule of a host material of the light-emitting layer have been anticipated.
An example of an iridium complex used as a light-emitting material of a phosphorescent light-emitting device, which includes a luminescent ligand having a naphtho[2,1-f]isoquinoline skeleton, is Compound E2 below disclosed in PTL 1. An example of another iridium complex including a luminescent ligand, which has a skeleton having one ring less than a naphtho[2,1-f]isoquinoline skeleton, and an auxiliary ligand is Compound A30 below disclosed in PTL 1.
